libxtables: move compat defines to xtables.c

Addendum to commit v1.4.3-rc1-41-g77f48c2 where the macro users
got moved.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
diff --git a/xtables.c b/xtables.c
index c898889..3c89a9d 100644
--- a/xtables.c
+++ b/xtables.c
@@ -39,6 +39,15 @@
 #ifndef NO_SHARED_LIBS
 #include <dlfcn.h>
 #endif
+#ifndef IPT_SO_GET_REVISION_MATCH /* Old kernel source. */
+#	define IPT_SO_GET_REVISION_MATCH	(IPT_BASE_CTL + 2)
+#	define IPT_SO_GET_REVISION_TARGET	(IPT_BASE_CTL + 3)
+#endif
+#ifndef IP6T_SO_GET_REVISION_MATCH /* Old kernel source. */
+#	define IP6T_SO_GET_REVISION_MATCH	68
+#	define IP6T_SO_GET_REVISION_TARGET	69
+#endif
+
 
 #define NPROTO	255